fix: resolve #1420 package.json parsing with two-step deserialization

src/manifest/mod.rs

@@ -7,6 +7,7 @@
 )]
 
 use anyhow::{anyhow, bail, Context, Result};
+use log::debug;
 mod npm;
 
 use std::path::Path;
@@ -625,16 +626,44 @@ impl CrateData {
         target: Target,
     ) -> Result<()> {
         let pkg_file_path = out_dir.join("package.json");
-        // Check if a `package.json` was already generated by wasm-bindgen, if so
+
+        // Check if a `package.json` was already generated by wasm-bindgen, if so,
         // we merge the NPM dependencies already specified in it.
         let existing_deps = if pkg_file_path.exists() {
-            // It's just a map of dependency names to versions
-            Some(serde_json::from_str::<HashMap<String, String>>(
-                &fs::read_to_string(&pkg_file_path)?,
-            )?)
+            let package_json_content = fs::read_to_string(&pkg_file_path)?;
+            debug!("Input package.json path: {:?} content:\n{}", pkg_file_path, package_json_content);
+
+            // NOTE: The previous logic failed because it attempted to parse the entire package.json 
+            // as a simple HashMap<String, String>. We now use a two-step parsing process:
+
+            // 1. Parse the entire file content into a generic serde_json::Value.
+            debug!("Starting full JSON parse.");
+            let full_json: serde_json::Value = serde_json::from_str(&package_json_content)?;
+            debug!("Finished full JSON parse.");
+
+            // 2. Extract the value associated with the "dependencies" key.
+            if let Some(deps_value) = full_json.get("dependencies") {
+                // The value must be a JSON object (a map).
+                if deps_value.is_object() {
+                    // Deserialize the dependency map (Value::Object) back into the
+                    // expected target type: HashMap<String, String>. This handles
+                    // the dependency merging downstream.
+                    debug!("Attempting to deserialize dependencies into HashMap<String, String>.");
+                    let map: HashMap<String, String> = serde_json::from_value(deps_value.clone())?;
+                    debug!("Successfully deserialized dependencies.");
+                    Some(map)
+                } else {
+                    // If "dependencies" key exists but its value is not an object, skip merging.
+                    None
+                }
+            } else {
+                // If the "dependencies" key does not exist, skip merging.
+                None 
+            }
         } else {
             None
         };
+
         let npm_data = match target {
             Target::Nodejs => self.to_commonjs(scope, disable_dts, existing_deps, out_dir),
             Target::NoModules => self.to_nomodules(scope, disable_dts, existing_deps, out_dir),
@@ -643,9 +672,10 @@ impl CrateData {
             // Deno does not need package.json
             Target::Deno => return Ok(()),
         };
-
+    
         let npm_json = serde_json::to_string_pretty(&npm_data)?;
-
+        debug!("Output package.json path: {:?} content:\n{}", pkg_file_path, npm_json);
+
         fs::write(&pkg_file_path, npm_json)
             .with_context(|| anyhow!("failed to write: {}", pkg_file_path.display()))?;
         Ok(())